Currently in bpftool's feature probe, we incorrectly tell the user that
all of the helper functions are supported for program types where helper
probing fails or is explicitly unsupported[1]:

$ bpftool feature probe
...
eBPF helpers supported for program type tracing:
	- bpf_map_lookup_elem
	- bpf_map_update_elem
	- bpf_map_delete_elem
	...
	- bpf_redirect_neigh
	- bpf_check_mtu
	- bpf_sys_bpf
	- bpf_sys_close

This patch adjusts bpftool to relay to the user when helper support
can't be determined:

$ bpftool feature probe
...
eBPF helpers supported for program type lirc_mode2:
    Program type not supported
eBPF helpers supported for program type tracing:
    Could not determine which helpers are available
eBPF helpers supported for program type struct_opts:
    Could not determine which helpers are available
eBPF helpers supported for program type ext:
    Could not determine which helpers are available

Rather than imply that no helpers are available for the program type, we
let the user know that helper function probing failed entirely.

[1] https://lore.kernel.org/bpf/20211217171202.3352835-2-andrii@kernel.org/

Milan Landaverde (2):
  bpftool: adjust for error codes from libbpf probes
  bpftool: output message if no helpers found in feature probing

 tools/bpf/bpftool/feature.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

--
2.32.0

Hello:

This series was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Wed,  4 May 2022 12:13:30 -0400 you wrote:
> Currently in bpftool's feature probe, we incorrectly tell the user that
> all of the helper functions are supported for program types where helper
> probing fails or is explicitly unsupported[1]:
> 
> $ bpftool feature probe
> ...
> eBPF helpers supported for program type tracing:
> 	- bpf_map_lookup_elem
> 	- bpf_map_update_elem
> 	- bpf_map_delete_elem
> 	...
> 	- bpf_redirect_neigh
> 	- bpf_check_mtu
> 	- bpf_sys_bpf
> 	- bpf_sys_close
> 
> [...]

Here is the summary with links:
  - [bpf-next,1/2] bpftool: adjust for error codes from libbpf probes
    https://git.kernel.org/bpf/bpf-next/c/6d9f63b9df5e
  - [bpf-next,2/2] bpftool: output message if no helpers found in feature probing
    https://git.kernel.org/bpf/bpf-next/c/b06a92a18d46

You are awesome, thank you!
-- 
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2022-05-04 12:13 UTC-0400 ~ Milan Landaverde <milan@mdaverde.com>
> Currently in bpftool's feature probe, we incorrectly tell the user that
> all of the helper functions are supported for program types where helper
> probing fails or is explicitly unsupported[1]:
> 
> $ bpftool feature probe
> ...
> eBPF helpers supported for program type tracing:
> 	- bpf_map_lookup_elem
> 	- bpf_map_update_elem
> 	- bpf_map_delete_elem
> 	...
> 	- bpf_redirect_neigh
> 	- bpf_check_mtu
> 	- bpf_sys_bpf
> 	- bpf_sys_close
> 
> This patch adjusts bpftool to relay to the user when helper support
> can't be determined:
> 
> $ bpftool feature probe
> ...
> eBPF helpers supported for program type lirc_mode2:
>     Program type not supported
> eBPF helpers supported for program type tracing:
>     Could not determine which helpers are available
> eBPF helpers supported for program type struct_opts:
>     Could not determine which helpers are available
> eBPF helpers supported for program type ext:
>     Could not determine which helpers are available
> 
> Rather than imply that no helpers are available for the program type, we
> let the user know that helper function probing failed entirely.
> 
> [1] https://lore.kernel.org/bpf/20211217171202.3352835-2-andrii@kernel.org/
> 
> Milan Landaverde (2):
>   bpftool: adjust for error codes from libbpf probes
>   bpftool: output message if no helpers found in feature probing
> 
>  tools/bpf/bpftool/feature.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
> 
> --
> 2.32.0
> 

Looks good to me, thank you

Reviewed-by: Quentin Monnet <quentin@isovalent.com>